As is known in the art, digital-to-analog converters have a wide range of applications. It is describable in some applications to produce a high power analog signal corresponding to a digital word. More particularly, in some applications it is desirable to provide a digital to analog converter that directly synthesizes high power analog signals at radio and microwave frequencies with high DC-to-RF power conversion efficiency. Further it would be desirable to provide such a digital to analog converter that may be used to accept a digital input and directly drive an antenna or other RF load without the need for additional power amplification (i.e. a software defined radio transmitter).
In accordance with one embodiment of the disclosure, a digital to analog converter is provided having: a source of a sequence of digital words, each one of the words having a decimal value n, where n is a decimal value between 0 and N; a thermometer code generator fed by the sequence of digital words for providing N parallel outputs, each one of the outputs having one of two discrete levels, the number of the outputs having the same one of the two discrete levels being a function of the decimal value n; an amplifier section having a plurality of N amplifiers, each one of the M amplifiers being fed by a different one of the N outputs of the thermometer code generator, each one of the amplifiers being driven into saturation in response to one of the two discrete levels or pinched-off in response to the other one of the two discrete levels; and a combiner for summing outputs of the N amplifiers producing a sequence of analog signals having levels related to the decimal values of the sequence of the digital words.
In one embodiment, the number of the outputs having a first one of the two discrete levels is a function of the decimal value n; and wherein each one of the amplifiers is driven into saturation in response to the first one of the two discrete levels.
In one embodiment, the digital words are produced with a predetermined pulse repetition frequency and wherein the sequence of analog signals is produced at said predetermined pulse repetition frequency.
In one embodiment, each one of the N outputs is a train of pulses.
In one embodiment, the amplifier section comprises a multi-input load-modulation amplifier.
In one embodiment, each one of the N outputs is a return-to-zero signal.
In one embodiment, a digital to analog converter is provided, comprising: a source of a digital word having a decimal value n, where n is a decimal value between 0 and N; a thermometer code generator fed by the digital word for providing N parallel outputs m1-mN, each one of the outputs having one of two discrete levels, the number of the N parallel outputs having the same one of the two discrete levels being a function of the decimal value n, the outputs m1-mN having said same one of the two discrete levels successively increasing with increasing decimal value n; and a plurality of amplifier sections. Each one of the amplifier sections comprises: a plurality of amplifiers; and a power combiner fed by outputs of the plurality of amplifiers. The digital to analog converter includes: a interconnection network for interleaving connections between the thermometer code generator and the plurality of amplifier sections; and a combiner for summing outputs of the power combiner of each one of the plurality of amplifier sections producing a sequence of analog signals having levels related to the decimal values of the sequence of the digital words.
In one embodiment, a digital to analog converter is provided, comprising: a source of a sequence of digital words, each one of the words having a decimal value n, where n is a decimal value between 0 and N; a thermometer code generator fed by the sequence of digital words for providing N parallel outputs m1-mN, each one of the outputs having one of two discrete levels, the number of the N parallel outputs having the same one of the two discrete levels being a function of the decimal value n, the outputs m1-mN having said same one of the two discrete levels successively increasing with successively increasing decimal value n; and a plurality of P multi-input load-modulation amplifier sections, AP, where p is an integer from 1 through P. Each one of the multi-input load-modulation amplifier sections, Ap, comprises: a plurality of N/P amplifiers coupled to the thermometer code generator; and a load-modulation network fed by outputs of the plurality of N/P amplifiers. Each one of the amplifier section AP is fed outputs mp, Mp+P, mp+2P . . . . Each one of the amplifiers is driven into saturation in response to one of the two discrete levels or pinched-off in response to the other one of the two discrete levels. The digital to analog converter includes a combiner for summing outputs of each one of the plurality of P multi-input load-modulation amplifier sections producing a sequence of analog signals having levels related to the decimal values of the sequence of the digital words.
The details of one or more embodiments of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.